Creating a clinical platform for carbon-13 studies using the sodium-23 and proton resonances.

PURPOSE: Calibration of hyperpolarized (13) C-MRI is limited by the low signal from endogenous carbon-containing molecules and consequently requires (13) C-enriched external phantoms. This study investigated the feasibility of using either (23) Na-MRI or (1) H-MRI to calibrate the (13) C excitation. METHODS: Commercial (13) C-coils were used to estimate the transmit gain and center frequency for (13) C and (23) Na resonances. Simulations of the transmit B(1) profile of a Helmholtz loop were performed. Noise correlation was measured for both nuclei. A retrospective analysis of human data assessing the use of the (1) H resonance to predict [1-(13) C]pyruvate center frequency was also performed. In vivo experiments were undertaken in the lower limbs of 6 pigs following injection of hyperpolarized (13) C-pyruvate. RESULTS: The difference in center frequencies and transmit gain between tissue (23) Na and [1-(13) C]pyruvate was reproducible, with a mean scale factor of 1.05179 ± 0.00001 and 10.4 ± 0.2 dB, respectively. Utilizing the (1) H water peak, it was possible to retrospectively predict the (13) C-pyruvate center frequency with a standard deviation of only 11 Hz sufficient for spectral-spatial excitation-based studies. CONCLUSION: We demonstrate the feasibility of using the (23) Na and (1) H resonances to calibrate the (13) C transmit B(1) using commercially available (13) C-coils. The method provides a simple approach for in vivo calibration and could improve clinical workflow.